18821221 has 8 divisors (see below), whose sum is σ = 19040000. Its totient is φ = 18604080.

The previous prime is 18821219. The next prime is 18821239. The reversal of 18821221 is 12212881.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 18821221 - 2¹ = 18821219 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18821021) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 53755 + ... + 54103.

It is an arithmetic number, because the mean of its divisors is an integer number (2380000).

Almost surely, 2^18821221 is an apocalyptic number.

It is an amenable number.

18821221 is a deficient number, since it is larger than the sum of its proper divisors (218779).

18821221 is a wasteful number, since it uses less digits than its factorization.

18821221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 819.

The product of its digits is 512, while the sum is 25.

The square root of 18821221 is about 4338.3431169053. The cubic root of 18821221 is about 266.0005888769. Note that the first 3 decimals are identical.

It can be divided in two parts, 1882 and 1221, that multiplied together give a palindrome (2297922).

The spelling of 18821221 in words is "eighteen million, eight hundred twenty-one thousand, two hundred twenty-one".